The present invention relates generally to sealed non-permeable fuel tanks for land-based, spark-ignition engine fuel systems. More particularly, the present invention relates to a fuel tank that vents emissions directly to the vapor port of a lawn mower spark-ignition engine.
Starting in the year 2011, Environmental Protection Agency (“EPA”) has requested that manufacturers find a solution to the issues of emissions. (See, Control of Emissions from Nonroad Spark-Ignition Engines and Equipment; Final Rule, 73 Federal Register 59034-59380, (Oct. 8, 2008)). As a result the EPA mandates that manufacturers of lawn and garden products meet new evaporative emissions standards and not have evaporation of reactive organic gases released into the atmosphere, by permeation emissions and by venting emissions.
At present permeation emissions result from the penetration of reactive organic gas molecules through the walls of fuel system components and evaporation of the gas molecules on the out side surfaces of fuel tanks, fuel lines, seals and gaskets. Steel tanks do not have permeation issues but the components used with these permit vapors to escape.
There are vented emissions which are also called or referred to as breathing loss or venting loss. These emissions come from direct evaporation of reactive organic gases such as gasoline from a liquid free surface into a gaseous phase which escapes from a fuel tank vent, a carburetor bowl, or other intake systems.
There are also running loss emissions which are fuel vapors expelled to the atmosphere as a result of fuel heating and agitation during operation.
Thus, for the start of 2011, EPA is requiring low permeation fuel tanks, low permeation fuel hoses, running loss controls, sealing and tethered caps called Phase 3 EVAP requirements. In the past fuel systems could have tank venting, fuel supply head, fuel consumption, and fuel vapor generation vented to atmosphere. These new requirements do not permit venting to air; in fact, the tanks must be sealed.
For conventional, present-day designs of fuel systems and tanks, fuel vapors are vented from a fuel tank to the atmosphere to avoid a build up of pressure in the fuel tank. In some instances, metal tanks have bowed out and plastic tanks have deformed in to more of a round shape when venting was not permitted. It is common practice to vent vapor in a fuel tank to atmosphere when an engine is not running to prevent the tank from reaching pressure limits on pressure in the tank and to prevent carburetor type engines from flooding.
Accordingly, there is a need in the art for a sealed non-permeable fuel system including a fuel tank that is not vented to the atmosphere.